问题
选择题
32.So often ______ in recent years that it has almost become a rule.
A．has this happened
B．this has happened
C．is this happening
D．for this to happen
答案
答案：A
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32.So often ______ in recent years that it has almost become a rule.
A．has this happened
B．this has happened
C．is this happening
D．for this to happen
答案：A